Should deepEqual use hasOwnProperty?

I found this out the hard way when a library was returning an instance of a constructor instead of a generic object. It looked the same via console.log, but the test was failing.

var Person = function(name) { this.name = name; }
Person.prototype.toString = function() { return 'My name is ' + this.name; }

var bob1 = new Person('bob')
var bob2 = { name: 'bob' }
expect(bob1).to.deep.equal(bob2) // false

The test output was pretty unhelpful:

  0 passing (32ms)
  1 failing

  1) semver-utils should parse good ranges:

      AssertionError: expected [ Array(1) ] to deeply equal [ Array(1) ]
      + expected - actual


      at Context.<anonymous> (test/spec.js:14:12)

It seems like the default deepEqual behavior should only check properties for which hasOwnProperty is true which is the behavior of node’s built-in assert.deepEqual. Or an alternative deepOwnEqual with that behavior should be provided.

[Sinewyk]

Hmm, I’m coming back to this because expect just moved from node-deep-equal to is-equal.

I would say best create a own flag

expect(A).to.deep.own.equal(B);

to emulate other behaviors as a opt-in. With the appropriate documentation it should be ok.

There’s still the matter of which library will power the own flag. Do we edit https://github.com/chaijs/deep-eql or use something else ? Ultimately your choice probably ^^.

[keithamus]

Thanks everyone for your input here.

We’ve added this to our Roadmap https://github.com/chaijs/chai/projects/2! We’ll be releasing chai 5 soon, but for now I’ll close this issue because it is tracked on our roadmap.